Fixing and simplifying background compiler benchmarks

[psfinaki]

2 of 8 benchmarks were broken here.

Method	UseGetSource	UseChangeNotifications	EmptyCache	Mean	Error	StdDev	Median	Gen0	Gen1	Allocated
ExampleWorkflow	False	False	False	6.248 s	0.3708 s	1.0150 s	5.761 s	5000.0000	1000.0000	6032595592 B
ExampleWorkflow	False	False	True	6.919 s	0.3501 s	0.9760 s	6.648 s	5000.0000	1000.0000	6143764208 B
ExampleWorkflow	False	True	False	7.086 s	0.1505 s	0.4318 s	7.074 s	5000.0000	1000.0000	6032798168 B
ExampleWorkflow	False	True	True	6.951 s	0.1351 s	0.2401 s	6.888 s	5000.0000	1000.0000	6144653048 B
ExampleWorkflow	True	False	False	NA	NA	NA	NA	-	-	-
ExampleWorkflow	True	False	True	NA	NA	NA	NA	-	-	-
ExampleWorkflow	True	True	False	7.376 s	0.3092 s	0.9019 s	7.344 s	5000.0000	1000.0000	6041351816 B
ExampleWorkflow	True	True	True	6.129 s	0.1767 s	0.5097 s	5.905 s	5000.0000	1000.0000	6151601544 B

After a brief consultation with @0101, decided to keep the benchmark for the exemplary purposes but to shrink it to the scenarios that work and make the most sense.

Current benchmark results on my machine.

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// * Summary *

BenchmarkDotNet=v0.13.2, OS=Windows 11 (10.0.22621.2861)
11th Gen Intel Core i7-1185G7 3.00GHz, 1 CPU, 8 logical and 4 physical cores
.NET SDK=8.0.100
[Host] : .NET 8.0.0 (8.0.23.53103), X64 RyuJIT AVX2 DEBUG
Job-ZMGPSB : .NET 8.0.0 (8.0.23.53103), X64 RyuJIT AVX2

InvocationCount=1 UnrollFactor=1

Method	UseChangeNotifications	EmptyCache	Mean	Error	StdDev	Median	Gen0	Gen1	Allocated
ExampleWorkflow	False	False	6.749 s	0.3663 s	1.0090 s	6.266 s	5000.0000	1000.0000	5.62 GB
ExampleWorkflow	False	True	6.729 s	0.2630 s	0.7502 s	6.410 s	5000.0000	1000.0000	5.72 GB
ExampleWorkflow	True	False	6.925 s	0.3304 s	0.9534 s	6.583 s	5000.0000	1000.0000	5.63 GB
ExampleWorkflow	True	True	6.656 s	0.2270 s	0.6366 s	6.433 s	5000.0000	1000.0000	5.73 GB

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